Comparative Development of Dwarf and Normal Segregants in Watermelon1

Abstract

A study of vegetative growth and flowering was conducted on normal and 3 dwarf segregants, dw-1, dw-2 and dw-1:dw-2 (extreme dwarf) of watermelon [Citrullus lanatus (Thunb.) Matsumura and Nakai]. Con pared to normal segregants, stem elongation was reduced by about 50% in dw-1 segregants, 80% in dw-2 segre gants and 90% in extreme dwarfs. The primary effect of the dwarf genes was an additive reduction in internode length. The rate of leaf initiation was reduced in dw-2 and extreme dwarfs, but not in dw-1 dwarfs. Extreme and dw-2 dwarfs flowered at an earlier node number than either dw-1 or normal segregants. However, due to slower growth and abortion of early pistillate flowers, particularly in dw-2 and extreme dwarfs, the dwarf segregants displayed a temporal delay in flowering. Hence, the late-flowering characteristic of the dwarf segregants, especially in dw-2 and extreme dwarfs, imposes serious limitations on their usefulness for breeding early maturing dwarf cultivars.